This invention relates to a storage apparatus.
For the purpose of achieving higher performance of a storage apparatus, there is provided a flash memory device (for example, solid state device; hereinafter referred to as “SSD”) using a flash memory that enables speedy access as a storage medium. The flash memory device includes a plurality of flash memory chips, and the flash memory chips each include a plurality of physical blocks. The physical blocks are units used for erasing data. In terms of characteristics of the flash memory, there is a limit to the number of times that erasure processing can be conducted for the physical block, and when the number of times of the erasure exceeds the limit, the block can no longer store data. Further, when a physical failure occurs in the flash memory chip, the data can no longer be stored as well. With the recent progress of a micromachining technology for semiconductors, the flash memory chip that enables recording with high density is manufactured, but there is a tendency that an occurrence rate of a failure is increasing and the number of times that the erasure can be conducted for a physical block is decreasing.
As a technology for improving reliability and availability of data storage on the storage apparatus including such a flash memory device, there is a technology that uses a plurality of flash memory devices. In U.S. Pat. No. 8,041,991 B2, there is disclosed a technology for copying, when a failure is detected in a physical block of a flash memory device, data of the flash memory device including a failed block to a spare flash memory device to replace the flash memory device.
In the technology of U.S. Pat. No. 8,041,991 B2, even when usable physical blocks in which no failure has occurred remain in the flash memory device involving the detected failure, the entire flash memory device needs to be replaced. This raises a problem in that the usable physical blocks that still remain cannot be used effectively.
Patent Literature 1: U.S. Pat. No. 8,041,991 B2